Cavity resonant excitation of InGaAs quantum dots in photonic crystal nanocavities

We have investigated cavity resonant excitation effects on InGaAs quantum dots (QDs) embedded in high-quality-factor photonic crystal nanocavities. The light emission of the lowest-order cavity mode at 1.06 mu m is enhanced by more than a factor of ten, as compared with nonresonant excitation, when the excitation wavelength is resonant with higher order cavity modes. This result can be attributed to an enhancement in the effective absorption coefficient due to a local enhancement of the excitation light, which couples with the cavity mode. The on-resonant excitation technique selectively and efficiently excites only the QDs in the cavity. On-resonant excitation at energies below the wetting layer band gap energy can achieve stronger light emission from the cavity mode than excitation at energies greater than the wetting layer band gap energy with much less undesirable background emission. It will be shown that this is primarily due to the enhancement in the effective absorption by the cavity resonant effect and the direct carrier generation in QDs.